Conventional driver's side airbag modules are mounted inside a motor vehicle's steering column. This is typically where the horn switch is located, and therefore the airbag module cover also serves as the area to actuate the horn. There are numerous horn switches which can be used in an airbag module cover such as variable resistors, piezoelectric devices and membrane horn switches as disclosed in U.S. Pat. Nos. 5,269,559; 5,157,372; 5,539,259; 5,369,232; 5,413,376; 5,520,412 and 5,575,498.
One horn switch that can be used is a force sensitive variable resistor switch, which changes its resistance when pressure is exerted on the switch. The change of resistance varies the resistors output voltage. Another switch is a piezoelectric device which transforms mechanical pressure exerted on it into an output voltage that is transmitted to an external horn circuit. A further switch is a membrane horn switch which conventionally comprises two thin conductive sheets which are separated by thin, small insulated spacers. Pressure on the switch causes the conductive surfaces to contact each other and close a circuit to actuate a car horn.
Multiple horn switches have also been assembled with the airbag module cover to increase the horn actuation area. Multiple horn switches are connected via a bridge member which serves as both as an electrical connection and a rupture area when the airbag is deployed, as disclosed in U.S. Pat. Nos. 5,585,606 and 5,684,283.
Coupling the horn switch to the airbag module cover is complicated and causes a number of problems. For example, when a horn switch is mounted on the back of an airbag cover, a significant amount of pressure is required on the air bag cover to actuate the horn switch. This can be dangerous in an emergency situation when horn actuation is quickly desired. Also, when a horn switch is inserted into a pocket of the airbag module cover, the switch may become detached from the airbag module cover upon inflation of the airbag and injure the driver because the horn switch can be ejected from the airbag module cover. Furthermore, the mounting of the horn switch to the back of the airbag module cover requires a significant amount of manufacturing time.
Therefore, it would be useful to provide an airbag module cover incorporating a horn switch that does not require an unreasonable amount of pressure to activate the horn, is not susceptible to becoming detached from the airbag module cover upon inflation of the airbag, and results in ease of manufacturing.